


Secret

by ConfusedMuse



Series: Soriel Week Stories [2]
Category: Undertale (Video Game)
Genre: Alternate Universe - Underfell, F/M, One Shot, Soriel AU Week, Soriel Week, Suggestive Themes, Underfell Sans, Underfell Toriel - Freeform
Language: English
Status: Completed
Published: 2016-12-27
Updated: 2016-12-27
Packaged: 2018-09-12 16:25:21
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 2,198
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9080317
Author URL: https://archiveofourown.org/users/ConfusedMuse/pseuds/ConfusedMuse
Summary: What had happened had shattered her, and there was no one else that could understand her pain. At the very least, Sans started to think, he could help her stay hidden away.But that wasn’t the only reason why, and he knew it.-Written for Soriel AU Week 2016 - Day 2: Underfell





	

**Author's Note:**

> Happy Soriel Week! Thanks to the holidays I'm a bit crunched for time, so I'm writing fics for Underfell and Underswap instead of doing fanart. Look forward to the Underswap one in a few days! But as far as this fic is concerned, I'm going off some of my own headcanons for Underfell, since--like Underswap--it started out as a design AU with no set story. I really like the idea of playing around with opposites in Underfell, since the focus is on it being dark and edgy, and I like to imagine what kind of choices the characters made to get to the point where they're portrayed in the AU. Hopefully everything I've presented in the fic is self-explanatory, but if you need any explanation on my headcanons, feel free to ask in a comment!
> 
> Thanks for reading!

The thick purple wood hung off its hinges and leaned against the rock wall behind it, deep stains of melted snow giving an appearance like teeth around the gaping dark hole that led deeper inside the mountain. The smell of something burning wafted out of the hole itself, the darkness inside not betraying what—or who—it came from. The deep claw marks above the entrance had caught some snow. Some stories said that, once, the insignia of the king hung there. Whether or not that was true was irrelevant now, however, because nothing was left now but the scar in the rock.

Sans stood a few feet away from the entrance to the Ruins, the wind in the forest tugging at the fluff on his jacket hood and the chain that hung off his belt. He sighed. 

“damn kids,” he muttered. “how many effin times have I told them—”

His grumbling was cut off by a yelp echoing out of the darkness. He sighed again, his breath creating a small smoke cloud around his skull in the cold. Shoving his hands deeper into his jacket pockets, he trudged forward, letting the darkness swallow him up as he passed under the damaged arch.

His magic eye flickered to life, casting a slight red glow on his surroundings. Sans knew the way, but he preferred avoiding the debris from the crumbling stonework.

He navigated his way around a piece of a collapsed wall that was bigger than he was, another light flashing up ahead. It faded away quickly, but Sans recognized it as a spark of fire. Yet another yell chased after it into the darkness, mixed in with the sound of a woman laughing. 

Sans readjusted his collar. He knew that laugh very, very well.

The woman's laugh preceded the flash of fire the second time, but Sans didn't hear any sounds of fighting aside from the short-lived blaze. She was toying with them, trying to scare them.

That would make this conversation a little bit easier.

Sans turned the corner, stepping into the flickering light that illuminated the rest of hallway. He could see the flame dancing on her palm, illuminating her sharp claws. The light caught on her fangs and horns as well, making her smile even more sinister looking in the half-light. Out of the corner of his eye socket, Sans could see the stupid teenagers he was looking for shivering against the opposite wall. He held back the urge to laugh, but let his mouth curl itself into a smirk.

Well, he _had_  warned them.

But even though he’d been looking for those kids, he didn’t take his gaze off of _her._  Sans deliberately kicked a chipped piece of stone in his path, sending it bouncing off the back wall with a loud cracking noise. 

She turned her head towards him, the fire expanding in her hand until it lit the corridor up like day. It detached from her palm, floating towards the low ceiling like a tiny sun. 

“Sans!” she said, his soul skipping a beat or two at the way she said his name. “I did not know you were coming to visit.”

He looked her over before answering. The shine in her white fur had gone dull. Her black robes had more rips and tears in the hem than he remembered from last time. And her eyes were shining a bit too brightly for Sans to feel confident anymore that she only intended to scare those kids away.

“i didn’t either, tori,” he said, talking to her like he always did. “but, uh, you’re kinda putting me in a rough spot right now.”

Her eyes widened even more—the length of her eyelashes always caught him by surprise—placing a hand to her chin. “How so?” she asked. “I have heard you warning these monsters away from my domain for a weeks now.” 

At the word “monsters,” she pointed towards them with her foot. The teenagers shrank away against the wall in fear. Sans noticed the movement but still didn’t look away from the boss monster in front of him. 

“So I thought that I would do you a favor,” Toriel continued with a smile and a shrug, “and just remove the problem entirely.”

One of the teenagers whimpered, and Sans had to admit that her smile grew more sinister with every passing moment. 

“i appreciate it, tori,” he said. “they’ve been a real pain in my spine.” He dropped his smile. “but things will get more complicated for me if you kill ‘em.”

Her face fell, looking like she’d told him that he didn’t like the flavor of pie she’d made. “What do you mean?” she asked. “If they can’t listen, then what good are they?”

Sans shook his skull. “as far as anyone knows, i’m the only monster who goes out this far into the forest,” he explained. “most of snowdin already thinks the screams are from me. which is pretty nice for my reputation, don’t get me wrong. but if they start thinkin’ that i’m offin’ _kids_ —”

“W-we’re not k-kids!” one of the teenagers piped up. 

Sans snapped his neck in their direction, eye flaring. “i’m _talkin’_  right now, _kid_ ,” he said. “unless you feel like removing yourself from the monster gene pool a little bit earlier than your friends, _shut up_.”

They shook their head and shrank back down next to the wall once more. Sans sighed and turned back to Toriel, who was watching him with a half-lidded gaze and a slight smile. He coughed.

“anyway,” Sans continued, “even with how effed up our world is, people still notice when a kid goes missin’.” He pointed with his thumb towards the teenagers. “and if these numskulls bite it, they’re going to think it’s me. and my bro—i mean, the boss is gonna wanna know all the details.” 

Sans kicked at the dirt on the ground, putting his hands back in his pockets. “if he snoops around even a little bit, he’s gonna find out about you,” he said. “and whatever he finds out, asgore will find out about it too. you’re gonna lose the option to be so selective with your house guests, if you know what i mean.”

There was a second where the only sound was the crackling of the fire above them. Then—

Toriel started to giggle. 

“what?” Sans asked, feeling a flush rise to his cheeks. He didn’t think he’d said anything funny, and yet—damn, did he love to hear her laugh.

“Do you really believe that Asgore does not know exactly where I am?” Toriel said between giggles, clutching at her stomach.

“uh,” Sans said, not knowing what to say. He’d never considered that. 

“I’m not a secret to him,” Toriel continued, her laughter calming down. “He can come whenever he feels like it. He just hasn’t yet.”

Sans stared at her for a moment, and then looked to the ground. For some reason, that had taken the rattle out of his bones, so to speak.

But in the next moment, Toriel’s hand had slipped under Sans’s chin, tilting his skull so that he was forced to look up at her. 

“You don’t like that, do you?” she whispered to him. “You want me to be _secret_  and _yours_  for as long as possible.” She laughed again.

That laugh. He’d been wrapped around her finger from the beginning. 

Sans had first heard it early on during his first patrols in the forest, where he’d paced back and forth between his station and the literal smoking hellhole, telling jokes to himself as a distraction from how boring the trek could be. He’d never expected an audience out there, much less a laugh.

First she’d just been a voice, able to match his jokes without a pause for thought. Then she’d stepped into the light and he’d realized all at once that those old tales about a queen who’d lost her mind had been true. From there, she’d started to invite him in, to get out of the cold, she’d say. The first few times she never let him farther than the first few steps outside the entrance, but with each meeting they walked further and further down, until—

He never asked her about what he’d heard from the stories, but Sans began to see other sides of her, the broken way she viewed the world. What had happened had shattered her, and there was no one else that could understand her pain. At the very least, Sans started to think, he could help her stay hidden away.

But that wasn’t the only reason why, and he knew it.

Sans shrugged as best as he could with Toriel’s hand still holding his skull up. “i’m just asking for a favor,” he said. “they're more of a problem for me dead than alive.”

She arched an eyebrow at him, letting his chin go with a smirk. “So it is not just about me,” she said. “You still cannot stomach the death of a child.”

“Not a child,” one of them muttered.

Sans sighed. “ya really wanna keep testing your luck?” he said, glancing at the group.

“But that is what I like about you,” Toriel continued, running a finger down his skull and across his jawline. “Underneath that tough act you put on, you still care.” Her red eyes glowed in the half darkness as the fire above them started to fade. 

“You have not given up yet,” she concluded with a whisper.

Sans shivered at the sensation of her claw moving across his skull. She really knew how to push his buttons. He wrapped his bony fingers over hers before she could pull away. “let them go, and we'll have some fun on our own,” he said.

Her smile widened. With a wave of her free paw, a small fireball floated down the hallway, lighting the way back to the forest. The teenagers stared after it for a moment, and then looked at Sans in unison with wide eyes.

Sans fought back the urge to finish what Toriel had started. Did these idiots have _any_  sense of self-preservation? 

“breathe a word of this to anyone, and I’ll throw you back in here myself,” Sans said. He flashed his eye a little brighter at them for good measure.The teenagers skittered away, heading back up the stairs towards the entrance. 

Before their footsteps had faded away, Toriel pulled Sans close to her chest, crushing her lips against his mouth. Sans’s hands drifted up the side of her face, deepening the kiss even more.

He did enjoy these moments. No expectations from his brother, no target on his back. She’s been right; he wanted Toriel to stay _his_  secret for as long as possible.

“Sans,” Toriel breathed, breaking away for a moment. “Now _I_  need to ask you a favor.”

He was still preoccupied with the way her hand was curled around his spine, but forced himself to focus on her words. “what is it?” Sans mumbled.

“When the next human comes out of the ruins...I want you to put them out of their misery,” Toriel said. She leaned down and kissed his clavicle.

“woah, woah, wait,” Sans said, pushing her back. “where the hell did that come from?”

She smiled at him. “It's going to happen sooner or later,” she said, her eyes oddly bright again. “And if for some reason I can't do it...I want to know that someone I trust _did_  take care of them.” 

She leaned forward, wrapping Sans in her arms. This time, all he could feel was her weight against him. “If they have to die,” she whispered, tightening the hug, “then I’d rather it not be Asgore.”

“who said that the next kid will die?” Sans laughed nervously.

“Because they always die,” Toriel said in that strange detached voice that always made Sans worry. She pulled back, sitting on her knees across from him so that they were close to eye level. “And I am so, so tired of being alone with that knowledge,” she continued. She took his hand in her giant one, her claws just barely scraping the surface of the bone.

“Promise me, Sans,” she said, her eyes burning through him. “I want you to join me.”

Yeah. He really couldn’t leave her alone.

He smiled at her, seeing his gold tooth glint in the reflection from her eyes. “just so that you know, i break all my promises,” Sans said.

Toriel laughed. “So what if I make you promise the opposite?” she asked.

“you and i both know that you don’t need to use psychology to make me agree to anything,” Sans muttered, closing her fingers over his with his other hand.

Toriel watched the movement in silence, giving his fingers a slight squeeze. “How true,” she said, glancing back up at him. “I suppose I will have to convince you in a different way.”

As she pulled him towards her again as the last bit of the light from the fireball vanished, all he could think was that there were worse things than falling into the darkness with her.


End file.
